This invention relates to a microwave amplifier and especially to a travelling-wave amplifier of coherent radiation at millimeter and submillimeter wavelengths.
Existing microwave amplifiers, such as conventional travelling wave tubes, are slow-wave devices having periodic structures of certain dimensions such that the structures are in resonance with the wave which is to be amplified. Thus, the physical size of the periodic structures must be varied in order to amplify waves of different frequencies. This feature limits both the tunability of conventional amplifiers and the ability of such amplifiers to accommodate high power as the wavelength becomes very small because smaller wavelengths require amplifiers with smaller, more delicate, periodic structures. Therefore, the power level of these devices falls sharply at millimeter and submillimeter wavelengths.